It is in fact useful to be able to estimate a height of water present on a road in real time so as to better appreciate the onset of hydroplaning.
Hydroplaning is characterized by the momentary presence of an amount of water between the ground making up the road and that part of the tire tread in contact with the ground. In this case, the film formed by the presence of water prevents all or some of this contact—there is no longer grip and therefore no longer force transferred between the vehicle and the road.
A film of water forms between all or part of the tire tread in contact with the ground when the flow rate of water flowing between these two surfaces becomes greater than the flow rate of water that the features of the road pavement and that of the tire can remove. This saturation effect is dependent on the height of water present on the ground and the speed of the vehicle.
The consequences of hydroplaning, during an acceleration by application of a driving force, during a deceleration by application of a braking force or during a change in direction, are considerable and can involve a partial or complete loss of control of the vehicle. It is therefore of paramount importance when travelling on a wet surface to be able to anticipate the conditions for hydroplaning.
To the driver of the vehicle, no warning sign precedes the onset of partial or complete hydroplaning—the danger is sudden and cannot be foreseen.
In addition, the water height measurement is information that can be taken into account by the various electronic assistance devices used, for example, for controlling an antilock braking system (ABS) of the vehicle, antiskid regulation (ASR) of the driving wheels, and trajectory control (ESP) or other forms of control or monitoring, such as for example the monitoring of tire pressure. Such information, coupled for example with a measurement of tire grip, would enable the effectiveness of these devices to be greatly improved in real time.
It is known from U.S. Pat. No. 5,502,433 to detect hydroplaning, but no mention is made of taking into account or estimating the height of water on the ground of the road. That patent merely involves observing a hydroplaning phenomenon beneath the tire, without providing a way to quantify it or even to determine one of the parameters of the origin of this phenomenon.